Fire alarm box lock



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Feb E2, w. J.' F. EBERT FIRE ALARM BOX LOCK v Filed sept. 25,. 1931 lim; pm

was ALARM BREAK GLASS @PEN mow @ULL HooK DOWN Patented Feb. 12, 1935 UNITED STATES` `FIRE ALaRM `Box LooK Joseph FfEbert, Hollis, N. Y., assignor to Signal Engineering & Manufacturing Company, New York, N. Y., a corporation of Massachusetts Applaation september 23, 1931, serial No. 564,674

5 claims. (c1. 711-14) 'I'he present invention relates to re alarm boxes and especially to boxes in which access to the interior of the box, in order topermit operation of the despatching mechanism thereinV for turning in an alarm, is obtained by breaking a cover glass, the door of the box then `being automatically released so that it may be opened and thedespatching mechanism set in operation. `VIn boxes of this type,rthe door to the box is held closed by a latch which is maintained in door locking position by al glassfplate forming the cover glas-s and located exteriorly of thebox;` jRemoval of the'glass, either by breakage or by intentional removal of the frame which holds ,the glass in position, releasesthe latch and threwdoorA is free to open, therebyl permitting access Atothe .despatching mechanism within' the box.

The object of the present invention is toV pro vide an improved locking Vdevice fora iire alarm box which permits the box to be readily opened for inspection, or repair, without removalof the cover glass which maintains the latch inlocking position. According to `the invention, the same latch, which maintains the door of saidvbox in closed position and which is automatically released when the cover glass is broken, is also-=ar ranged to be released by other means accessible from a point externally oi the box and operating independently of the cover glass, lso that the door may be readily opened by an inspector without removal of the glass. Other objects and advantages of the invention will appear from the fol-.

lowing detailed description taken in connection with the accompanying drawing, in whichz- Fig. 1 is a front elevation of the fire alarm box, the door of said box being closed.

Fig. 2 is a front elevation similar toFig. 1, therk door of the box being open. n i, Y

Y Fig. 3 is a section along the line 3-'.3 of Fig. 2. Fig. 4 is a fragmentary elevation of the inside of the cover or door for the box, parts being broken away to show the structure by which the latch is opened independently `of the cover glass. Fig. 5 is a fragmentary view similar'to Fig. 4, illustrating the manner in which the latch is opened upon breaking the cover glass. l

Like reference characters refer to like parts in the different iigures. v

Referring particularly to the drawing, a iire alarm box 1 has a door 2 on the face .thereof hinged at 3 on said box. Within the box is provided the usual despatching mechanism having an actuating lever 4 projecting through the front Wall of the box so that it may be conveniently operated by the person "desiring to turn in the,

alarm after the door 2 has beenopened, see Fig. 2. The door 2 is normally held in closed position by a latch device indicated generally at 5, which is arranged to vengage a stud 6 projecting from the front Wall'of the box. The stud 6 is provided, asshown in Fig. 3, with a conical head '7 to permit the latch to ride thereover as the door is closed, as will be hereinafter pointedV out, and a shoulder 8 directly back of the conical head '7 to: prevent unintended withdrawal of the latch from said stud after thedoor is closed. The latch 5 is arranged to be held in closed positio-n by a cover glass 10, the latter being retained in position on the door of the box by a frame 11 attached to the door 2 by screws 12..

The latch device 5 comprisestwo substantially parallel arms 13 pivotally mounted on pins 14 on the inner side of the door 2. The upper vends of said arms 13 are yieldingly drawntoward each other by-a spring 15, the ends of which are connected to said arms 13, and since the arms 13 are pivoted below the spring 175, the latter tends to separate the lower or stud engaging jaws 16 of said arms and withdraw them from engagement with the shoulder 8 on the stud 6, as shown in Fig. 3. The upper ends 17 of the latch arms 13 arev maintained in spaced relation against the tension of the spring by a conical portion 18 provided on the inner end of a plunger movable in the Vdoor 2, the outer end of said plunger 2G being engaged by the inner surface of the cover glass 10, Fig. 3. l The cover glass holds the conicalportion 18 between the upper ends 1'7 of the arms 13 in the position of Fig. 2, thereby separating the arms and maintaining the lower jaws 16V of said arms in, engagement with the stud 6. Upon breakage o the cover glass 10, the conical portion 18 is squeezed between the latch arms to move the plunger 20 forwardly of the box (to the right, as shown in Fig. 3), the arms 13 being drawn together bythe spring 15. Thus the lower jaws 16` of said arms are withdrawn from the purpose, a cam 21A is mounted for rotation on the Y inner side of the door 2 of the box', said cam being journaled in the doo-r of said box and having an opening 22 therethrough for the 'reception of a suitably shaped key. As shown in Fig. l, the key opening 22 is accessible from the outside of the cover 2, so that theY key may be inserted at any time when the box is closed. As shown most clearly in Figs. 2 and 4, the cam 21 is located between the arms 13 substantially midway between the pivot pins 14 and the lower stud engaging jaws 16 of said arms, and is oval or elliptical in shape. Consequently, when the cam 21 is in the normal position of Fig. 2, the arms 13 operate in response to the plunger 20 and entirely independently of said cam. When, however, a suitable key is inserted in the opening 22 and rotated through an angle of substantially the cam is rotated into the position shown in Fig. 4, and the lower jaws 16 of the arms are separated, thereby releasing the stud 6 from said arms so that the door may be opened. The arms 13 are provided with transverse slots 23 for receiving the pins 14, so that when the cam 21 is rotated' to unlock the door 2, the arms 13 may pivot about the conical portion 18 of plunger 20 against the pull of the spring 15, the pins 14 then sliding in the slots 23. Guide members 24 extend transversely across the arms 13 of the latch to retain said arms in position, vand to allow the sliding movement of said arms in response to cam 21.

During the normal functioning of the latch,

the spring 15 which draws the upper ends of the arms together holds the arms against the pins 14 in the position of Fig. 2, so that said arms pivot about said pins to disengage the stud 6, as shown in Fig. 5, when the plunger 20 is released by breakage of the glass l0. When the arms are actuated by the cam 21 with the plunger 20 held by the glass 10, the location' of the spring is such that the upper ends of the armsare then held in pivotal engagement with the conical portion 18. rlhe spring 15 further provides a yielding connection between the arms, so that when the door 2 is closed with the arms 13 held in stud engaging position by the plunger 20, said arms may rst be forced apart by the conical head 7 of stud 6 and then be returned to locking engagement with the shoulder by said spring.

From the foregoing, it is apparent that by the present invention there is provided an improved door locking device for fire alarm boxes which is effective to hold the door securely closed while the cover glass remains unbroken. At the same time, however, the locking device Vis Vso constructed that the door can be opened for inspection of the box mechanism by an authorized person having a suitable key. This unlocking of the door for inspection in no way disturbs the normal functioning of the locking device under the control of the cover glass, since closing of the door` after an inspection restores the box to its normal condition wherein it is necessary to break the glass in order to open it, without the inspectors key.

I claim,

1. In a locking device for a door, a fixed stud, a pair of latch members pivotally mounted on the inside of the door, a frangible member mounted on the outside of the door, a plunger having oneend engaging said frangible member with its other end holding opposed ends of said latch members apart to maintain the opposite ends of said latch members in engagement with said stud to hold the door closed and a cam disposed between said latch members on the opposite side of their pivots from said plunger and turnable from the outside of said door into a position in which it spreads said latch members to disengage them from said stud and permit the door to open while said frangible member remains unbroken.

2. In a locking device for a door, a ilxed stud, a pair of latch members pivotally mounted on the inside of the door, a frangible member mounted on the outside of the door, a plunger having one end engagingv said frangible member with its other end holding said latch members apart and turned about their pivots to maintain their opposite ends in engagement with said stud to hold the door closed, and a cam disposed between said latchmembers on the same side of their pivots as said stud, said cam being turnable from the outside of said door into a position in which it turns said latch members about said plunger to disengage them from said stud and permit the door to open while said frangible member remains unbroken.

3. VIn a locking device for a door, a latch member pivotally mounted on the inside of the door, a frangible member mounted on the outside of the'door, a plunger extending through the door for turning said latch member in one direction about its pivot to hold the door closed while one end of said plunger bears on said frangible member, and a member operable from the outside of the door for turning said latch member in the opposite -direction about said plunger, as a pivot, into a position in which the door may be opened.

4. In a locking device for a door, a latch member pivotally mounted on the inside of the door, a frangible member mounted on the outside of the door, a plunger extending through the door for turning said latch member in one direction about its pivot to hold the door closed while one end of said plunger bears on said frangible member, and a cam member turnable from the outside of said door for turning said latch member in the opposite direction about said plunger, as a pivot, to release the door while said latch member 'is still engaged with said plunger.

5. In a locking device for a door, a fixed stud,Y

a pair of latch members pivotally mounted on the inside of the door, a spring tending to pull opposed ends of said latch members together, a frangible member mounted on the outside of the door, a plunger having one end engaging said frangible member with its other end forcing opposed ends of said latch members apart against the pull of said spring to maintain opposite ends of said latch members in engagement with said stud to hold the door closed, and a member operable from the outside of the door for turning said latch members about said plunger, as a pivot, to disengage them from said stud and permit the door to open while said frangible member remains unbroken, said spring also serving to turn said latchmembers about their pivots to disengage them from said stud upon release of the plunger through breakage of the frangible member.

JOSEPH F. EBER'I. 

